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If a helicopter's tail rotor fails, is it possible to perform an emergency landing?
In the event of a total failure of the tail rotor, is it possible to maneuver a helicopter to an emergency landing spot that is within, say, 30 minutes flying time?
What are the maneuvers required for a pilot to fly reasonably straight, and how do the aerodynamics work?

Tail rotor failure procedure is well described on FAA Helicopter Flying Handbook, page 11-16: Antitorque System Failure. It will rely on high forward speed and autorotation to somehow limit the aircraft spin. As the vertical rate will be around 1500 to 2000 fpm, this anyway forbids a 30 mn flight.

Not really. The rotor design is to keep the helicopter from not spinning around in circles. The helicopter would most likely spin around and crash.

@Ethan.  It is perfectly possible to recover from a tail rotor failure.  There are some flight regimes that might lead to a crash with all but the best pilot and some luck.  A tail rotor failure in cruise should be survivable, especially if you can find something hard to land on.  The killers are hovering out of ground effect and low altitude, high speed.

I don't think 30 minutes is possible. A better question might be, how far can an auto-rotating helicopter go? This will depend on many things, of course, and you can't just multiply the cruise speed by the time of descent because I'm pretty sure the forward speed during auto-rotation is much less than full cruise speed, so it would be an interesting and non-trivial question.

As it turns out, this has actually been done before for almost thirty minutes. See Earp's answer and his link for the story. I think we all got fixated on auto-rotation, as usually that's what you must do immediately when the tail rotor fails, but main engine can still run despite tail rotor failure and forward flight can be maintained with weathervaning under the right conditions. Hopefully it is still safe to say that actual auto-rotation cannot be maintained for 30 minutes.

Although I used to think this was impossible, I now believe this can be done using weathervaning.
At a fast enough forward speed, the airflow will naturally keep the helicopter facing in that direction. For an example of someone doing this in reality, for an almost identical time period that OP requested, see this link:
http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=10493099
According to the link, he needed to maintain 80 knots forward speed to prevent it from rotating out of control. Note whether this is possible may well depend on the weathervaning charactistics of the particular helicopter.

This is a very nice find, all the more so for someone new to the site. Welcome to aviation.SE!

=autorotation see my awnser below

Not an R-44 in the photo but what a story!

Yes, but you certainly could not fly for 30 minutes since to do so, you would need power and if you use power, you will spin with no way of stopping it. Apart from a catastrophic failure, this is probably the hardest thing to get right.  A tail rotor failure on approach or in a high hover or with speed close to the ground is probably not going to end well.
The correct recovery is to enter auto rotation.
Since this removes the torque from the rotor, the fuselage will not spin apart from that caused by drag in the transmission system which can be countered by keeping speed up and using a little opposite cyclic. The tail boom and vertical stabiliser will tend to keep the aircraft straight whilst there is significant forward speed.  Any tendency to spin is opposed by the air flow striking the tail boom and fin on the side opposite to the spin and correcting it.
The problem comes from the landing since you cannot balance torque as you raise collective and increase lift (and therefore drag which increases torque) to arrest the descent.
The solution is to tweak the throttle to control torque.  However, a high speed run on landing is inevitable.  Hope for a strong wind that you can land into since this will reduce the touch down speed and help to keep the approach and touchdown straight.
In a hover, roll off the throttle and keep it there then perform a hovering autorotation.
In both cases, keeping the throttle rolled off is the key.  If you bring significant power from the engine back into the rotor system, you will spin uncontrollably.  Small amounts of throttle, rolled rapidly on and off can be used to control torque as can use of collective during the descent of an autorotation.
I hope this one never happens to me.  Engine failure doesn't particularly worry me, nor do "stuck pedals" but a tail rotor failure would not put a smile on my face.

I don't think the exact answer is 'yes but hard to achieve.' The OP was asking for a landing up to 30 minutes flying time away. I don't think any auto-rotation can last that long, but it can certainly save your life. Exactly how far you can go during auto-rotation is probably not the best priority you're concerned with during an emergency, but nevertheless seems to be what the OP is curious about.

Yep, mins has that covered in his comment. No way could you get 30 mins with no tail rotor since the only way to stop the spin (and therefore keep going forward) is to take power off which means you are going to land soon. From typical cruise altitudes < 1 km.

@DrZ214 Wow, see Earp' answer.  So someone has done it.  Amazing pilotage.  I didn't know about this incident and if asked before, would have said impossible.  You learn every day...

@Simon in Bristow flight 56C a lightning strike damaged the tail rotor. All people on board survived the autorotation landing on the sea.

@Simon Ah, I was misunderstanding the exact scenario. The article linked to in Earp's answer says only the tail rotor failed, so apparently the pilot flew on for that long because the engine and main rotor were fine and he used the rudder in forward flight to maintain yaw. In this thread I was assuming the main engine had to be shut down, but after re-reading the OP, I see he's only asking about tail rotor failure.

@DrZ214 Helicopters don't have rudders.  Yaw control is provided by the tail rotor so if this fails, the primary yaw control is gone.  He managed it by using the weather cocking affect of the fuselage and fin and by tweaking throttle and collective.

As a helicopter pilot with over 3,000 hours I can assure you that landing with a tail rotor malfunction is possible and that I have given over 100 check rides where I made students land with stuck pedals or simulated total loss of thrust.
As with many other questions it all depends on the type of helicopter.  If it has an adjustable fuel throttle, you can reduce the fuel flow while making a powered approach to a landing. In other helicopters with FADEC, you can make powered approaches using combinations of crosswinds and air over the tail to make a safe landing.  For a total loss of thrust you'll probably land in excess of wheel limitations, but even if pop all the tires you'll still walk away.
As far as flying 30 minutes to land-since we aren't in authoritative flight it's possible...but I wouldn't advise it because of the nature of Tail Gear Box issues.  If it's eating itself up, will it stay attached and in one piece?  How much will that shift weight and balance?  Will it catch fire?

Actually lost a tail rotor. On a UH-1 in 1971.  Slung a blade, ripped off the gearbox, destroyed the driveshaft.  Occurred at about 80 knots.  Aircraft has a tendency to nose forward and obviously no yaw control.  Control was very tenuous.  Since you won't know exactly what's going on back there, suggest you autorotate.  That's what I did.  It was a normal auto again, with a tendency to want to roll forward so you have to keep control movement slow and smooth.  Pulled pitch a little lower than normal and just concentrated on keeping the aircraft as level as possible at that point.  Aircraft did about 1 1/2 rotations before it settled in.  Slight spread of the skids.  Aircraft survived and I had to change my underwear.

Welcome to Av.SE, and thanks for an interesting first-person account of how such an emergency landing is possible.

Do you mind sharing the registration, or any investigation report. Would be interesting to see how it happened

I have no experience flying Blackhawks but I was an aircraft maintenance officer on the good old UH-1 "Huey". If you have tail rotor failure during normal foward flight yes you can continue to fly until you run out of fuel.
You need to maintain at least 60k of foward airspeed and the vertical fin will help keep you from spinning.  You can remove the throttle from auto and use the twist grip to use the torque of the main rotor to help turn the nose, this is especially helpful (no make it necessary) during a running landing (landing like a fixed wing aircraft).
Control gets worse if the tailrotor gearbox separates from the tail and even more difficult if you loose part or all of the vertical fin.
If you loose the tail rotor while landing and you are well below 60k airspeed and close to the ground, you then enter autorotation. Once you remove pitch and go to flight idle on the throttle the aircraft slows or even stops spinning.
Tail rotor failure procedures and landings were practiced by all pilots during aircraft check rides under the supervision of an instructor pilot.

What is "60k"?  Is that 60 km/h or 60 knots?

I would have to say it’s knots. The poster writes like an American. Plus, 60 km/hr sounds way too slow to fly without rudder input. At 45-60 kn, the much smaller R-22 needs very little peddle input. Though at 10 hours, I have not tried any tail rotor failure procedures yet.

K stands for knotes in charts.

I agree with several responders that in some aircraft unlimited forward flight is possible with some types of tail rotor failure.
As a former Crew Chief of a marine corps Sikorsky UH-34d in July of 1967 in Vietnam Nam
Our pilot flew to a safe landing about 15 minutes after ground fire severed our tail rotor cable. This particular aircraft ( I understand) was capable of “weathervaning” at speeds above about 55 knots using proper cyclic and throttle control as it had a rather large tail surface. In this case the pilot landed at +-55 knots without autorotation—- hit the brakes and pulled back the cyclic and brought us to a stop otherwise undamaged—— it was a hairy landing, I can assure you. The Squadron was Marine Medium Helicopter-263 flying out of Ky Ha.

Ex Army UH-1 pilot (Vietnam)...
In a UH-1 losing a tail rotor at speed say greater than 60 knots does not require an immediate autorotation. The aircraft will weathervane quite nicely.
With a UH-1 you can fly it onto the runway. I forget the suggested touchdown speed but it was fast enough so that you were still weathervaning. Yeah, there are a lot of sparks...
I was an IP and this was a part of every checkride. Practiced on a regular basis from flight school on.
If the nearest field was 30 minutes away that would be technically feasible although as has been mentioned there are arguments for getting it down much earlier.

The correct answer is maybe!
I learned to fly in a Hiller OH-23 in 1969. We practiced running landings assuming loss of control cables or stuck pedals utilizing throttle for directional control.
The Hiller has a very large tail boom surface which allows slipstreaming, hence fairly decent directional stability.  BUT we never practiced assuming loss of the blades and/or the gearbox!  Remember, the tail rotor is also a rotary wing but in a vertical orientation. Most helicopters do not have the needed surface area in their stabilizers to offset the loss of the wing/lift effect of the tail rotor.  My hat goes off to any pilot that can lose the tail rotor and make a landing without rolling the helicopter into a little scrap metal ball.
I own a Rotorway 162F.

Yes, it is possible to make an emergency landing in a helicopter should a tail rotor failure occur.  The procedure is that same as that of a engine failure and it's called an autorotative landing.  Essentially a powerless helicopter becomes an autogyro (gyrocopter) in flight and can be flown as such.  This is a common emergency procedure taught to students working on a pilot certificate for a rotorcraft-helicopter.

Yes.  They’re called autorotation landings and specifically used in the event of either an engine, transmission or tail rotor failure.  You will not get that long in the air as helos executing auto rotations come down like a brick!

How is this different from your previous answer?

A loss of tail rotor effectiveness in cruise flight is manageable. The vertical fin is cambered in the form of a wing in order to "fly the tail" in some manner. It is imperative to keep a minimum speed of 40 kts to keep the tail effective. For the ASTAR AS350B3E helicopter, the "book" calls for you to continue flying to a landing zone and then to kill the engine at an altitude high enough (more than 1,000') to sustain an autorotation. Once you kill the engine you will reduce the torque thus reducing the need for the tail rotor. Other schools of thought are to keep the engine on and to head to an airport with a decent sized runway and to fly down the runway at 40kts or more and then kill the engine and slow at the same time. You will spin.


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How airworthy was the BV 141?
How did the BV 141 fly? It looks like it has very uneven weight distribution and the overall design is asymmetric. I'm surprised that it could even take off.

See also: https://en.wikipedia.org/wiki/Rutan_Boomerang

Curious that the horizontal stab is so truncated on the right side. Why would the do that?

The weight from the cockpit on the right is balanced by adding weight with one horizontal stabilizer on the right and no horizontal stabilizer on the left.

More than the weight of the cockpit, I think it's positioned that way to avoid turbulence from the cockpit. If you have clean air on one side of the aircraft why not use it? The imbalance due to the down-force being off-center doesn't matter as much as you'd think.

@RalphJ: To improve the field of view and to give the rear gunner less of a chance to disable his own aircraft.

Why would you think the weight was not correctly distributed? If the center of pressure and the center of gravity coincide, there is no problem. Every pilot needs to bring the center of pressure right above or below the center of gravity when flying; this is commonly known as trimming the aircraft. Almost all aircraft have small asymmetries which need to be counteracted by small control surface deflections or trim tab settings.
Note that the fuselage of the BV-141 is offset to the left and the cockpit is offset to the right. This keeps the spanwise center of gravity location near the center of the wing, so any resulting rolling moment is small. What remains (maybe due to an unusual high or low loading of the cockpit) can be trimmed away with the ailerons. A yawing moment due to asymmetric thrust can also be corrected by rudder trim, and the engine was placed on the left so the p-factor of the propeller (which creates more yawing moment at low speed) would counteract the yawing moment due to its out-of-center position.
The BV-141 was designed as an observer platform with an unrivaled field of vision. By using an offset fuselage, only the left side was obstructed by an engine or tailboom. If you compare the BV-141 with its competitor for the same tender, the Focke-Wulf 189, the advantage should become obvious.

Focke-Wulf Fw-189 (picture source)
Note that the BV-141 was a private entry in this contest and was not selected.
A similar aircraft with an asymmetrical mass distribution was the Flyer I of the Wright Brothers. Here, the right wing was 4 inches wider than the left to create additional lift for the heavy engine which was positioned to the right of the pilot.

Front view of the 1903 Flyer I (picture source). Note the offset engine position.

Thank you for not only answering the given question, but the unwritten one, "why in the heck would they do that???", as well!

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Why did Cessna use a new design for the C162, instead of updating the C150 design?
As I stare at the ceiling unable to fall asleep, airplanes are on my mind.  Failed airplanes.  Specifically: the Cessna 162.
I understand that Cessna perceived a need for a two seat trainer.  The CEO himself called that out: "The need for a modern, cost-effective two-seat trainer aircraft has never been greater, and we believe we are well positioned to meet that need."  I also understand that the light-sport aircraft (LSA) market was thought to be a significant driver for aircraft sales.  That turned out to be a gross miscalculation.  Cessna ended up selling 192 Skycatchers (versus a planned run of 600 per year) due to quality and price misses.  About 80 were not sold and retained as parts donors.  A fleet of ready-made LSA aircraft already existed (Champs, Chiefs, Cubs, T-Crafts, etc) so the value proposition of a new $150,000 LSA runabout was not compelling...or so it seems.
The following question assumes that there are folks on SE.av that have some industry knowledge of the GA manufacturing scene...
Why did Cessna not just resuscitate the proven 150 line (~24,000 built) and forego the LSA segment, given that the objective was to capture the two-seat training market and a good number of very cheap LSA airplanes already existed?
I recognize that there may be no good answer for this.  Maybe it was just one of those plausible-at-the-time business moves that didn't pan out.

I agree.  There is no good answer.  Perhaps I'll write what we already know.  LSA came as a political move.  Recreational existed.  Perhaps people came looking for money and made lots of it and the little airplanes paid the price.

You use the abbreviation LSA a lot but what does it stand for?

@Notts90 Light Sport Aircraft

I think there are a couple reasons: 1) Weight, and 2) the Type Certificate.
For #1, the original C-150 is roughly 100 lbs too heavy (in empty weight).  That's a bit over a 10% reduction, which is huge in an all-aluminum design.  Note that later models need even more weight removed (C-152 included).
For #2, the C-150 is a CAR Part 3 type certificated design.  To sell it as a LSA would almost certainly require a re-designation so as not to conflict with the original type certificate.  This is primarily a paperwork thing, but nobody had done it before (even now, none of the "grandfathered-in" type-certificated designs are still built under their type certificate or by the original manufacturer).  The C-152 is an add-on to the C-150's type certificate, so the same problem applies to it.
As far as why the C-162 failed, I think Carlo's answer covers most of the reasons pretty well (ignoring the "GA is dead" rant), though I'd like to add that Cessna did a terrible job with designing the C-162 and took so long to "get it right" that they didn't start deliveries (of an arguably inferior product) until right after the 2008 economic downturn.

Hello ioctLR, welcome to Aviation.SE!

GA really is all but dead, dude.  Until the middle class again decides that it likes flying and actively pursues it, that's not going to change.

Agree on the weight, but why even shoot for lsa given the large number of legacy lsa airplanes?  Also, I think blaming "the lawyers" is a red herring.  As far as the CAR3 cert, many planes manufactured today are built using CAR3.

acpilot, good question...  A Cessna exec could answer it, but I can't.  I'm sure they thought they could compete well in the LSA space, and new is always preferable to used (ignoring budget constraints), so they probably thought it would be a good market and just flubbed the implementation.

@acpilot Ignoring kits, to build a two-seat 'mass market' aircraft you have two options: an LSA or a type-certified aircraft. An LSA avoids the full type certification process and uses cheaper (and more modern!) avionics etc. Re-using the 150/152 would mean restarting a production process that closed 30 years ago, or going for a completely new type cert. Either would be hugely expensive, and I guess Cessna decided the LSA way was best, i.e. most attractive to customers and most profitable. That's my summary of what I've read, I may be wrong :-)

Actually the 162 is almost 300lb lighter than the 150. That's a 25% weight reduction

@acpilot Regarding the CAR3 status of most GA aircraft, I agree...  There have only been a handful of part 23 certified ASEL piston aircraft ever (too expensive), and of those, I can only think of 3 that are currently available new (Cirrus SR20/SR22 and Cessna TTx).  I probably missed one or two smaller players, but literally everything else is homebuilt, LSA, or CAR3.

@TomMcW, you are correct, but I was referring to what needed to be done (at the minimum) to the original C-150 to meet the LSA requirements.  Since the C-162 is a clean-sheet design, the weight reduction vs. the C-150 is largely irrelevant beyond illustrating the futility in just bringing back (and modernizing) the C-150.

But that's specifically the question. Why a new design rather than tweaking the old. 25% weight reduction is beyond any possibility of tweaking it. Even at that weight it baaaaarely squeaks in under the LSA limit.

Ah, I understand your point now, and fully agree. I figured the C-150 (at 986 lbs) would be "do-able" as LSA with two 170 lbs adults and 15 gallons of fuel, which is an empty weight of 890 lbs and would allow for 2 hour training flights. Obviously the C-162 does a much better job...

Short answer: GA is effectively dead and the middle class killed it.  That segment of the population went from enjoying aviation to deciding that small aircraft were capricious and dangerous little recreational vehicles and were scared of and wanted nothing to do with flying.  And with that came the lawyers who nearly sued every GA manufacturer out of business.  And the complaining homeowners, greedy real estate developers and politicians who began shutting down airports, etc.  What was left was a very small number of very wealthy and intrepid flyers who were willing to spend a lot of cash on personal aircraft and the last group of die hard GA flyers and home builders.
Everyone in the GA community erroneously thought the reason no one went into flying airplane's was that they were too expensive.  The solution?  Go back to the days of the Piper Cub and other light aircraft powered by a small engine and minimal instruments and avionics.  Surely this combined with new composite materials, ballistic parachutes for safety and modern avionics would attract new pilots.
Unfortunately, nobody in the personal aircraft market wants to buy an LSA with a minimum of creature comforts and limited performance.  GA manufacturers thought they could attract a new generation of flyers using LSAs, but buyers shyed away from simple airplanes and selected ever more feature filled and exotic varieties.  Most LSAs sold today are featuring glass cockpits and are often equipped with autopilots and are IFR certified and costing over $170,000.  This poor market research combined with farming out the manufacturing to China and the problems associated with that arrangement is what killed the Skycatcher.
And I hate to say this, but the Skycatcher wasn't that great of an LSA.  It wasn't a bad airplane, but it seemed rushed and lacking the attention to detail that many other LSAs had.  The plane was made in a communist country and the dark gray spartan sheetmetal interior combined with uncomfortable, tiny seats to sit in matched those origins to a tee.  I compare this with both the Czechworks SportCruiser and the Evektor SoprtStar LSAs which were much, much nicer airplanes in the same price range.  The 162 flew well and had good handling characteristics albeit it landed pretty fast for an LSA.  But again, the market really didn't want that kind of an airplane.
In truth, GA is about freedom and LSAs just don't offer that.  In their pure form they are a simple solution for the guy who wants to make a few laps around a traffic pattern on a Saturday afternoon.  But they really don't fulfill that niche market for the personal freedom of flight or a practical means to travel with.  And again if GA is to survive it requires a serious interest from the middle class who want to buy large numbers of affordable aircraft, something that just doesn't exist.
As to resurrecting the C-150/152 line, that should have been Cessna's first move but management seemed convinced that a clean sheet design offered better market share (wrong).  But Cessna learned the hard way about the economics of LSAs and it is doubtful they will try again in the near future.

Given that the middle class is shrinking, and getting squeezed, your blaming the middle class for this is a curious stance to take.  I find your analysis otherwise rational.

This started back in the mid 1980s when GA aircraft were relatively affordable to the middle class.

I disagree that GA is dead...  It hasn't yet recovered from the 1980's litigation-fest, but that's largely because every "recovery" was knocked down by outside events (9/11, '08 housing bubble, etc.).  Considering 3rd-class medical reform and the (nearly finished) part 23 re-write, and I think GA is ripe for a major comeback...

I would disagree to say that they were "relatively affordable" to middle class in the 80's. Take for example the 1981 172P, $33,950 was the retail price, which was almost $90,000 in today's dollars. While much cheaper than the $270,000+ cost of a new 172 today, buying a $90,000 toy wasn't any more affordable in the 80's as it is in the 2000's. Even in 1956 when the 172 was introduced, it cost the same as the average home.

But it is relatively affordable to a middle class or an upper middle class person who earned around $30,0000-$40,000 annually in those days.  They may have to save a little for the airplane, but the could still afford them.  And a new C-172SP these days retails for $420,000 depending on options.

True enough, and I think that's why the market for new type-certificated aircraft is so slow.  On the other hand, the vast majority of new ASEL piston aircraft registered in the US today are E-AB or E-LSA homebuilts.  You don't see those in the market statistics...  GA is far from dead, it just looks different.

Honestly, the value proposition of something like that vs. something like an RV-8 is a no-brainer. Not only can you outfit the RV with as much or as little crap as you want, it has unbeatable price per performance numbers. GA is still there, but homebuilt is owning the low end of it.

Disagree that GA is dead.  Someone is buying PC12s, TBMs, King Airs, various Cirri, etc.  Maybe the GA segment that relies on 1940s technology is dying, but it's not dead yet.

Acpilot- A Cirrus SR2X starts at 500,000 USD.  The other aircraft mentioned cost over $4.5 million.  Not exactly affordable to say an electrician with an interest in flying.

@acpilot, while those are valid GA airplanes, anything with a turbine engine of any kind has never been in the "middle class" price range.  For this discussion, I don't think they are significant.

GA is GA.  If we're talking about the low end of GA, ok.  Still not dead, but dying.  It's so much easier to buy/finance a fifth wheel and some dirtbikes.  No training, recurrent training, maintenance, and the whole family can enjoy it.  Once a family realizes how simple flying really is and once the economics of a partnerdhip are explained, low end GA is more attractive.  How to cut through the perception of the "rich person" hobby though?  That's a different question entirely, however.

Well that 'low end' of GA is the lion's share of the business.  Airports all over the country depend on their business to stay afloat and run flight schools.  When that low end of GA dies, so do these businesses.  Sure the major outfits like Signature or larger airports survive - and do so by catering to wealthy pilots or business aviation but it radically changes - and effectively kills what we thought GA was.  Now this wouldn't have happened, as my original thesis states, if there was a major buying market for affordable aircraft existed and that has to be done by middle class buyers.

Downvoting because of the middle-class rant. The reasons for the decline of GA is not the subject of the question.

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How does single-sided deafness affect the different pilot licenses?
About 12 and a half years ago I lost the sense of hearing in my left ear due to borreliosis. However, I have always wanted to get a pilot's license at some point in my life. I am aware that for some (or even all?) licenses, a medical examination must be passed and one-sided hearing loss is essentially a no-go.
So my question is: What are my possibilities with my disability? What kind of license could I still be allowed to get or will I have to bury this dream?
I live in Germany.

If you were willing to travel to the US (which is not all that uncommon to get a pilots license) and get your license under the FAA regulations you could do it as per the regulations,

§67.305   Ear, nose, throat, and equilibrium. Ear, nose, throat, and
  equilibrium standards for a third-class airman medical certificate
  are:
(a) The person shall demonstrate acceptable hearing by at least one of
  the following tests:
(1) Demonstrate an ability to hear an average conversational voice in
  a quiet room, using both ears, at a distance of 6 feet from the
  examiner, with the back turned to the examiner.
(2) Demonstrate an acceptable understanding of speech as determined by
  audiometric speech discrimination testing to a score of at least 70
  percent obtained in one ear or in a sound field environment.
(3) Provide acceptable results of pure tone audiometric testing of
  unaided hearing acuity according to the following table of worst
  acceptable thresholds, using the calibration standards of the American
  National Standards Institute, 1969:

The way this is written if you can score at least 70% in one ear on the audiometric speech discrimination test you should be good to go. Note this is for a class 3 medical with will not allow you to fly commercial operations. I am not sure how the new basic med requirements fall into all this but your best if you have specific questions is to contact an AME directly.
From a practical standpoint, the cockpit of most small planes is fairly defining already and the headsets take mono signals from the radios so I don't really see how the lack of binaural hearing would present any issue.

Thanks a lot, this is already very helpful and encouraging! However, I just read that I will not be able to fly D-registered airplanes with it and would probably have to fly N-registered planes (Link). Of course, I will be able to convert it to the German PPL(A), but I am not sure, if I have to get a medical re-evaluation. I did write to a local medical examiner, though, as you advised. Thanks!

@basseur I belive you can fly and more importantly have an N-Registered aircraft in Europe. I belive there are some questions around it on here somewhere.

Alright, I will look into it. Thanks again!


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Is any readback required when ATC uses the phrase "RADAR CONTACT"?
As the title says, is a readback required? I've heard some people say that it's not required, while some others say we should readback our call sign only. Some even say just push the transmission knob twice to inform the controller that we are acknowledging.
Which one is the correct action and what are the references or publications?

Which country are you asking about? Requirements, regulations and local practices can be different in different parts of the world.

I'm not sure that this is a dupe. The question @fooot linked to asks "what does it mean" but this question asks "is a readback required". Those seem like quite different questions to me.

@Pondlife the linked question also includes "what would be the appropriate responses"

"Reading back", i.e. repeating what ATC said to you, is only required for clearances and hold-short instructions, when it's critical that ATC knows you understood them.  A simple "radar contact" message is neither.
Most other things, you just "acknowledge", which can be done by saying your callsign or clicking the mic twice.  (ATC usually adds "roger", which is a holdover from Morse code operators using "R" as a shorthand for "received"; most pilots don't bother.)  This is done so ATC knows you heard them, but for non-critical things that don't require a readback.  If you don't acknowledge, ATC may keep repeating it until you do, which is annoying both to them and to everyone else on the frequency; acknowledge promptly so they can move on.
However, when they say "radar contact", they will usually include additional information such as the position of the contact, altitude, etc.  You only need one acknowledgement for the entire message.  Note that if the position or altitude they say is incorrect, you really need to tell them that, because it means they're looking at the wrong radar target--and that could get you or someone else killed.  Acknowledging is an implicit confirmation that they're looking at the correct target.
If they give instructions or ask questions as part of the same message, then you would reply to those as you normally would; you don't need to separately acknowledge the "radar contact" or other informational parts because it's assumed you heard them if you're replying to other parts of the same message.

To add, if you are calling an approach controller and they issue a squawk, then call "radar contact," no follow-up is required. If you are departing a towered airport and are instructed to contact departure—and you do—and they say "radar contact"—THEN you should respond with some sort of acknowledgement, even just your callsign, to close the two-way communications loop (now each party is sure that the other was able to hear them).

No. It is an information by the controller to let you know that you have been heard & identified. As he doesn't pass any relevant or critical information, there is no need to readback.
The same goes with e.g. wind information given by ATC.

That’s not how we do it in US airspace. Do you have a source for your assertion?

In the US (Boston, MA, area), it usually comes across as "Nxxxxx, radar contact, xx miles south of (location, like the airport you just departed from), altimeter xx.xx", and we would reply, "xx.xx, Nxxxxx".

In my case, when I've been hand over to SHANGHAI CTRL, which is in CHINA, the controller only acknowledged with "callsign, SHANGHAI CTRL, radar contact." most of time. According to DOC. 4444, it mentions only INSTRUCTION, CLEARANCE, ALTIMETER SETTING, SSR CODE, etc., that need to read back. What confuse me is that if I don't read back, some controller will say again in case I don't  get them. However, if I'd like to read back, I can't find the reference that I can read back with call sign or simply click mic twice.

@JScarry If the ATC passes any other information such as altimeter right after the radar contact phrase, then you usually readback as the call includes critical information. However, here in Europe, ATC very rarely passes any information that might be important within the radar contact acknowledgement.

@JScarry - do you have a source for your assertion? Proving a negative is hard, and I promise you most controllers don't care if someone doesn't say anything after "radar contact" if no further instructions are provided. (In the US).

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


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B777- In emergency mechanical back up how does the flight controls manage engine failure
In case of engine failure above the ocean with multiple electrical failures and after having exhausted the batteries the fly by wire mechanical backup with available hydraulics if left with the THS and one spoiler per wing under the control of the control wheel, How in these conditions the pilot will manage the asymmetrical thrust?
Basically thrust asymmetry is normally managed with the rudder, the schematic shows in mechanical backup the rudder is not Available, while the remaining spoilers 4 and 11 are rather for roll control, what can do the pilot?
N.B. June 17, 2019: if it is difficult to imagine one engine failure + total electrical failure, please imagine an engine failure + Total FBW computers and controllers failure, the most important is to go into the mechanical mode as described here below with an engine failure:

@ymb1, thank you very much, so it looks for Airbus it is part of the mandatory training, if you find something similar for the B777, it would be very helpful as I imagine the mechanical backup is not done for nothing but for exceptionally rare cases, so what I need is a hint on how the pilots will fly it in such a case.

I don't understand your scenario. If you have only a single engine failure, the other engine will produce enough electricity via its IDG. You only lose all electrical power for both engines failed, APU failed, RAT broken and batteries exhausted.

@Bianfable, the scenario is total loss of electrical power in order to match with the mechanical backup. However to reach this tragedy I am assuming an engine failure and multiple other troubles since more than an hour to exhaust the batteries. The second engines generators, The RAT, the APU, troubles etc, to match the total loss of power. What is important is how will the pilot fly the aircraft In mechanical backup mode.

@user40476 In that case I'm not sure if the remaining engine would continue to run, since the FADEC needs electrical power to operate. How would you even control that engine without electricity from the flight deck?

@Bianfable, as you know each FADEC has its own miniature generators on its own engine, however if you prefer consider one engine failure with Flight Control Computers failure, the important is to go into the MECHANICHAL CONTROL mode, mode imagined by Boeing, not by me

Your question is kind of confusing. I think you're asking "If the rudder isn't working, then how can a multi-engined airplane manage the asymmetric thrust from an engine failure?" The answer to that question is "by rolling toward the good engine". This produces a turning moment opposite to that produced by the engines.
If that isn't enough, then there's nothing the pilot can do to fly in a straight line. The pilot may be able to control the radius of the turn by rolling and/or adjusting the throttles, and so make slow progress in a series of loops toward some airport, but the airplane is going to turn in this situation.
If an engine fails, flying with a slight bank toward the good engine is in fact the recommended procedure for most multi-engine airplanes, even if you have full rudder control. There's actually a mnemonic for it: "Raise the dead", because the dead engine is going to be higher than the good one. It's more fuel efficient and produces less strain on the airframe then trying to correct with rudder, because the fuselage is lined up with the airflow. As for passenger comfort, well, you're going to need a minimum of four separate failures to get into this situation, so by that point, passenger comfort is well down the priority list.

@HiddenWindsgield, The trouble is that apparently from the schematic in case of total electrical loss including the batteries being exhausted the mechanical backup concerns only the THS, and two spoilers 4&11, Should we loose all electrical power one may assume having lost one engine in addition to other troubles. So how will the pilot fly the B777 in this case. ymb1 has done a very interesting comment to the question but his comment applies to the Airbus 320; I am not finding something similar that applies to the B777.

I think your confusion, @user40476, comes from this incorrect assumption: "Should we loose all electrical power one may assume having lost one engine in addition to other troubles". Losing one engine does not cause loss of all electrical power. You'd have to lose both engines, the APU and the RAT would have to fail, then you'd have to exhaust the batteries. With one engine operable, both the current answers provide info on how the plane would be handled.

@user40476 It's possible to lose a generator without losing the associated engine. So, no, you cannot just assume that electrical issues mean engine failure, just like you can't assume that engine failure means electrical issues. So far as I can tell, your question boils down to "What do you do if the rudder isn't available, and you've lost an engine?", which I've already answered. I guess you could also be asking "Why doesn't the B777 have a mechanical backup for the rudder, in case of engine loss?", to which the answer is "because rolling toward the good engine works just fine".

@FreMan, I am assuming the loss of an engine in order to consider an asymmetrical thrust condition, and I am assuming the total electrical loss to go into the Mechanical Control mode, if you prefer you may consider an engine failure + FBW Computers failures, the important matter is not the exact scenario but just to consider the functional operation of  the Boeing Mechanical Control mode with an asymmetrical thrust. The  comment given here above by ymb1 is very interesting but it applies to the A320 not to the B777, I do need a similar answer but applicable to the B 777.

@HiddenWindshield, great, you are putting the exact situation and the scenario is not important, Indeed irrespective of the cause, if we get into Mechanical Control condition and we have lost an engine, how to fly this aircraft. You have indeed answered by saying rolling toward the good engine works fine. I feel I am obliged to accept it meantime, but I find the matter very hazardous with passengers behind the technical crew, really why Boeing didn’t add a mechanical backup to the rudder? This aircraft is so perfect, I can’t imagine this weakness. There must exist another solution.

@user40476 I'll add that to my answer, along with some other info.

@HiddenWindshield, yes indeed make it an answer and I will accept it, so irrespective of the scenario, you are answering to the question given in the title: « B777: In emergency mechanical back up how does flight control manage engine failure? »

@user40476 I've edited my answer.

In your scenario there would likely still be hydraulic power and electrical power from the one running engine and the RAT (Ram Air Turbine) generator, which can power everything except the autopilot. The TAC (Thrust Asymmetry Compensation) system would compensate for the asymmetric thrust.

@ Juan Jimenez, In the question I am saying « available hydraulics » but no electrical power.  The mechanical back up is designed for the cases of total electrical loss otherwise it wouldn’t have been implemented for nothing. Nevertheless,Please don’t change the scenario. If you think it is probabilistically impossible, you may sayit as a comment but not answering to an other scenario.

If you want to create wild imaginary scenarios, at least try to think up something reasonable. It is almost impossible for the RAT to not work as designed, and hence almost impossible for there to be zero electrical power. You drop it out and wind produces electricity. That's what it is designed to do. Please do not try to change reality. The mechanical backup is not designed just because someone thinks there will be total electrical loss, it's also used in normal operations.

And yes, I know what you will do, edit the original question after the fact to support your late "argument" of why you don't like the answers given to you. That's why I will ignore this question from now on.

@ Juan Jimenez, Thank you, you are so kind


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Can an ultralight aircraft fly with a 18hp engine?
I have some questions - I'm planning on building single seat UL aircraft with this plan sketch (I have more), I drew this based on real plain and some research. Empty weight is between 50-70kg with engine
The power plant I will use this engine. 4 stroke, OHV, single cylinder, 440cc, power 18hp/3600 RPM, torque 3.0 kgm/2500 RPM (21.7 lb ft), ignition TCI, gross weight 37 Kg.

My questions:

Is this engine enough to make it fly?
Do I need belt reduction or gear reduction for a 1 meter propeller?
What propeller size to fit with this engine?
Do you see any problems with this design?

https://en.wikipedia.org/wiki/AmEagle_American_Eaglet
I found this on Wikipedia, it use a McCulloch MC101 15HP engine with 9000 RPM, that's make me doubt to use SFE 460 because the RPM far bellow. I can't find McCulloch MC101 here

say plane and engine is 100kg and you are 100kg, that's around 2000N in total, say you have a lift/drag ratio of 10 then that's 200N of drag. WIth 13KW you are looking at max vorticity of 65 meter/second or 230km/h and that's pretty fast. So the direct answer to your question is yes if you do everything right.

Everything right being you limit the total weight of the system to 200kg, you included, and make the wing to have lift to drag ratio above 10 and has enough lift to cruise around 100km/h, and efficiency of prop and transmission is above 50%. But the other question is, how do you take off? You need extra power to accelerate to take off speed within finite length of the run way, and you need more lift than gravity to accelerate vertically from the ground. That could more than double the requirement for power unless you have assisted launch or just use air drop.

@May be as you say, but you'll meet your ceiling as soon as you are out of ground effect...

The Rutan Quickie would cruise at 185 kph with 18hp!

The fuselage is too short. Make sure that the horizontal tail has more lever arm!

Keep in mind that aviation engines, while expensive, have some important differences like safety compared with normal gasoline engines as explained here: https://aviation.stackexchange.com/questions/11527/what-are-some-of-the-differences-between-piston-engines-used-in-aircraft-and-aut/11528#11528

I suggest that you get a copy of NACA report #408 from the web. General Formulas and Charts for The Calculation of Aircraft Performance This was develop to quickly do preliminary studies of new military aircraft in the era between WWI and WWII.

Should very well be possible. The Wright Flyer had an empty weight of 274 kg, and an engine that developed 12 hp, so you're way ahead there.

As for the propeller, you want the tips not to exceed critical Mach number because of the increase in drag for no gain in thrust, so tip speed needs to stay below 340 m/s. At max torque RPM of 2,500, your engine is doing 262 rad/sec. The drawing shows a prop with diameter 1.2m, resulting in a tip speed of 262 * 0.6 = 157.2 m/s or Mach 0.46. A bit low, longer blades would be better. No need to gear down.
It may be a bit impractical to use a propeller longer than 1.2m, best to use the largest standard diameter propeller that can be accommodated. Of course, the engine will need to be able to reach 2,500 rpm, where its maximum torque is developed. Required torque and thrust go up with RPM$^2$, torque goes up with $R^3$, thrust only with $R^2$. Large propellers convert the horsepower into maximum thrust better, and this is the area where the Wright brothers made optimal use of the available horsepower, driving two 2m, slow turning propellers.
An "educated" guess at torque & thrust here. I would say you'd need the longest standard size propeller that is your craft can accommodate without hitting the ground during TO/landing, with the highest pitch available. If 1.2m is max diameter you may want to use a 4-bladed one.

have you ever built an ultralight aircraft?

No mate I have not, and have no interest in doing so.

Did I read your post wrongly? I found in wikipedia regarding the AmEagle, the power plant is 50HP (37kW). Powerplant: 1 × Continental A50 air-cooled, horizontally opposed, four-cylinder piston engine, 50 hp (37 kW) Is this different aircraft?

@AirCraftLover Please check the Wikipedia article for the Wright Flyer.

It's possible to arrive at a rough estimate by assuming that the L/D ratio is 9. Now, the empty mass is 70 kg. Let's add 45 kg for the engine, transmission and propeller. And we must not forget the mass of the pilot (85 kg) and 20 kg of fuel. It's a total mass of 220 kg. Let's round it to 250 kg in order to be on the safe side.
If we imagine the plane gliding at L/D = 9 and 25 m/s, the sink speed will be 25/9 = 2,78 m/s. As the mass of the plane is 250 kg, its weight is 2450 N. Thus, the 'gravitational power' involved in the glide is 2,78 x 2450 = 6805 W.
The plane, for straight and level flight, will need exactly that power. If we assume that the transmission and propeller losses are 50%, you'd need twice that power, that is, 13,6 kW. Besides, some extra power is needed, (in order to climb, for example...) so let's increase the figure by 30%. 13,6 x 1,3 = 17,68 kW = 24 hp. That's the engine power that, in theory, and according to this simplified estimation, would be needed for that plane...

Op indicated 70kg with engine. Taking back the 45kg for the engine its 155. Rounding to 200kg, using your method I get 14.2 hp.

with a 18hp engine definitely YES, specially designed planes flew with human power only. With that specifical 18hp engine probably yes but extensive adaptation may be needed and reliability of the thing may end up being sub-optimal.

very clear and simple analysis, thanks for this!

Short and simple answer to your question is, YES, there are numerous ultralight AIRCRAFT that are flying with 18hp rated engines (and less - hp) and have been for years.
I understand from your questions and comments that you are completely new to this aspect of flying, and it is understandable that you will have questions; you would be foolish not to (have questions).
At the same time do you really want to fly or just kick tires and dream about it ?
Most of the people getting into this FACET of aviation will research the various offerings available and most will purchase maybe two or three plan sets to better understand what comprises a viable aircraft; I own ten PLANS for the following - Proven Aircraft: Bower's Headwind, Evans Vp-1 Volksplane, Sorrell SNS-2 Guppy, the Sky Pup or Mach None, and the Beaujon ENDURO, as well as the Chotia Woodhopper; also have plans for the Mitchell Wing, Easy Riser and Quicksilver (weightshift) gliders that were both built and flown, as gliders only. Oh yeah almost forgot my Bensen Gyro-Gider, a total blast !
I settled on building the SNS-2 Guppy with a 1972 750cc BMW engine since it is enclosed and I am too old to enjoy freezing my butt off in an open frame type ultralight. THE BMW engine was chosen because it is more than reliable and I own two of them, A No
Brainer, plus I don't have to cut down a VW two get half as much HP as the BMW produces.
At this point in time I hope you have come to understand that the purpose of an ultralight is SIMPLY to get into the air, get out of the pattern and fully enjoy
FLYING in a machine that truly permits you to be a part of the experience, same
Reason people ride motorcycles instead of driving a car - to experience your surroundings to the fullest.
Forget all the mathmatic mumble-jumbo such as as nose/tail moment ratios and WING loading, etc., etc AND find out which ones have a GOOD support system still available.
Then and only then pick the one you believe will suit your interest, and build it - to the plans, If you want to fly it more than ONCE !
Best of Luck.  LW

I tend to build the aircraft and of course after it finish and tested, the flying experience is the reward of building it, but thanks for your response. i have bought a plan for Affordaplane and now i'm looking for suitable engine for it. I see one that might ok for it, but still not sure until i get the engine and test with the propeller. It's 2 stroke 150cc, 28HP. I know Affordaplane uses 35-40HP engine, but they have tested using rotax 277 28HP engine, i think i can use an engine that similar to rotax 277 power since my weight is pretty light and also try to reduce some other weight

I would get away from Wright Brothers comparisons and listen to Peter.  Lengthening the fuse will give you a much smoother feel with the elevator and more pitch and rudder control.  Reminds me of the time when Richthofen recommended to same thing for the new Fokker D.VII.
As an added bonus, it will help keep your CG in the right place when you add a bigger engine.
Although torque from overpowering would be dangerous, 18 hp may be a bit anemic, particularly into the wind.  At lower power you have to go with lower wing loading.  The wind will blow you around like a leaf.  Also, lower flying speeds leave much less of a safety margin in the event of a gust or wind shear.  More power can save you in these situations.
Research of other, proven aircraft of this plan form may show 30 - 50 hp may be more realistic.  Good luck with your work.

Thank you for the response. I've been thinking of another engine. It's two stroke, single cylinder 150cc. The company claim in produce 28HP, but many people "dyno test" the engine, they got 30+ HP. The problem is that motorcycle engine and water cooled, i'm still looking for more suitable engine, because this type of hobby is not really popular here nor even exist yet. The proper engine for aviation is out of my budget, something like snowmobile engine is what i looking for. The airplane design is not really a problem. I have some interest with Affordaplane and Legal Eagle.

@Gifhary Syidhqa Hamim  while gathering funds for your project, you may wish to continue to study plan forms.  Unless you are into aerobatics, lengthening to fuselage will make it much easier to control.  A matter of preference I guess.  As far as engines,  this is the heart of any powered aircraft.  The one you pick needs to handle the prop load without overheating.  The first thing you buy may be the prop.  Then bench test your engine candidates and see what rpm you can get, and if possible, how much thrust.  Then you can decide if this is the best engine for your plane.

Your drawing doesn't provide enough detail to give a definitive answer.  The design looks similar to something like an Legal Eagle.  Those generally use a half VW engine putting out about 40hp so I don't think that motor would be up to the task without building it up some.  If you are married to that design the good news is there is a whole universe of parts and detailed instructions for these types of motors thanks to the popularity of gokart racing.
The wisest way to go would be to download plans for an ultralight which has already been extensively flown and had the bugs worked out.  Or if you're dead set on doing your own thing download a few sets of plans for different gliders, then figure how to add a motor.  I know the Goat glider has free plans and people have successfully added a motor to it.
I'm building a modified Bloop 4 ultralight right now.  It's designed for an 25hp paramotor engine, so engine wise if you remove the governor from yours you should be there. You can check it out here: http://m-sandlin.info/bloop/bloop.htm
The same dude designed the Goat so you can grab those plans there too if you like?
I've found these pages helpful as I've built my own ultralight. The first one is for RC's but works equally well for paramotor/ultralights.
Static Thrust Calc
http://www.godolloairport.hu/calc/strc_eng/index.htm
If you do remove the governor from your motor you can play with different props/reduction drives here:
Culver Propellers
http://www.culverprops.com/pitchselection.htm

i already change plan to another engine, 2 stroke and 28 HP. My problem with 2 stroke is just too much eating fuel, but yes the engine are pretty light and powerful

Your question is "Can an ultralight aircraft fly with a 18hp engine?"
The answer is yes an ultralight can fly with that engine and you will not need a reduction drive with the correct sized prop designed to keep tip speed subsonic.
Check out the beaujon ultralights, the bloop motorfloater by Mike sandlin and the rutan quickie. Three different planforms and they all fly on hp in that range.
The  beaujon enduro seems closest to yours and used a 16 hp engine and was heavier. Its Briggs and Stratton engine  ran in the mid 3000s rpm range max output and lower than that at cruise.  It appears to have the same power output profile as yours.
There's a wiki page for the enduro and the beaujon site sells plans and a manual on how to design your own ultralight.
Whether YOUR ultralight will fly who knows. Come back and post updates!

Yes, a True Part 103 Ultralight and even some Small Kitplnaes can fly on 18hp. That's 18hp@3600rpm. That Engine uses a very Small 22mm/24mm Carb and a Restrictive Air Filter and Restrictive Exhaust with a Low 8.0-8.3cr. Put just a 32mm Carb Mukuni Flat Side Carb, with K&N Air Filter, and a Tuned Header Exhaust, and it will probably make around 25hp@3600rpm. If you add a Hi Rev Kit, disable Governor(Always for Plane use), disable Low Oil Sensor(Always for Plane use), and add a better CAM, it can make 35+hp@5000rpm. I would always use a Reduction Belt Drive.

Your answer looks OK but why all the strange capitalisation of words that shouldn't be (unless you were writing in German)?

That capitalisation doesn't even work in German. They rather combine the words ... like Flatsidecarb :)

I'd can say you can make it to fly, just attach an adjustable propeller in order to achieve the exact torque for a lift and constant speed.

Welcome to Aviation.SE! Can you provide some more information to your answer and maybe, if you have some, your sources?

MTOW Weight in KG/10kg x 1kw = hp needed.
Example: MTOW 600 lbs = 272.2 kg / 10kg = 27.22 x 1kw = 27.2 kw = 36.5 hp.
So Plane Weight + Your Weight + Fuel Weight + any Bags weight = MTOW.

Hi and welcome to the site. This rule of thumb you refer to would benefit from some sources or explanations regarding its reliability. As it stands it is clear that some aircraft break it, for example the Wright Flyer described in another answer.

18 HP is more than good enough. Wright Brd's proves it. Your plane seems perfect. However, %35-40 of the propulsion will be lost as "fuselage drag", where your HP's are valuable .
If you can split the power into two, like that in the "Colombon Cri Cri". (You can do it with proper Gates belt drive), you can use lighter props (0,7m) and nacalle drag loss will be limited to %15.
Good luck.

Do you have some sources to back up the answer?

I don't understand why balancing your power on 2 propeller improve "fuselage drag". You must extend this part.


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Is 'cost sharing' different between jet and prop powered aircraft?
I half remember, sometime in the past, there were different costs in turbine powered aircraft that were allowed to be put into the bucket for cost sharing.
Do I remember correctly or incorrectly?
If this a correct memory, what are the additional shareable costs in a turbine powered aircraft?
addendum:  My ancient brain has come up with some vague answers.
IE, the hourly payments for engine and airframe maintenance.  This was comparable to rental cost, but because  it is a defined amount in a turbine totally owned by the pilot, it was quantifiable.

Are you thinking of 91 Subparts F and K on fractional ownership? There's some stuff in there about cost sharing.

Not fractional ownership. Straight Part 91, sole ownership.  The difference between a Cirrus 22 and a Cirrus 50, for example.

I give up.  I have searched and can find no reference in the FARs concerning this question - just the current one about pr0-rate sharing that we all know and love.
Perhaps the 91F and 91K parts have replaced the vaguely remembered item from the 1980s.
Thank you for the opportunity to ask.


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Where can I find United 757 Checklists? (CRM, Pre Start, Pre Takeoff)
Where can I find United 757 Checklists (CRM, Pre-Start, Pre-Takeoff)? I need these for a writing project that I am doing. Any help is greatly appreciated. Thanks in advance!
Thanks, Charlie :)

If you need those specific and current checklists your best bet is to ask them directly with a heartwarming story and hope - but given that they cost a lot of money to make I don’t like your chances. You might be able to find ones created for flight simming which might not be 100% accurate but close enough.

Make friends with a United pilot flying 757s?

I doubt that you can get an airline specific checklist for an airplane, but for Boeing 757-200, a generic one is available. Please note that they might be for simulators (as Ben mentioned) but are close enough.

PDF
Trello
X-Plane (screenshot below)

Did you find these in X-Plane 11? Where did you get them?


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Is there a mathematical formula to find the most efficient propeller?
Is there a mathematical formula to find the most efficient propeller? Is a five-blade better than a four-blade? Does software exist to aid in the calculations there?

Also related: What are the advantages of more than 4 propeller blades?

Possible duplicate: https://aviation.stackexchange.com/q/8907/1379 ("Wouldn't there be a mathmatically 'best' design?")

Yes. The first good ones were published by A. Betz and L. Prandtl in 1919, and the latest substantial improvements were added by Larabee. Those formulas are the basis of Mark Drela's XROTOR. It will give you the chord and twist distribution over span for a prescribed speed, torque or thrust. It is best used for lightly loaded propellers - if you need anything with activity factors (power absorbed by the propeller per blade area) above that of purely subsonic airplanes, better consult prop manufacturer tables.
Generally, the most efficient propeller will be large, have two blades and will spin slowly. Depending on flight speed and desired thrust, you will need to reduce diameter, increase speed and add blades as required, at the price of lower efficiency.


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Which avionics suite does the 757 use?
I am wondering who makes the 757 avionics? Is there a glass cockpit upgrade? What is the name of the avionics suite?
Thanks in advance

You know, at the time the 757 was considered to be a "glass cockpit" but yes, there is a more modern upgrade.

The original 757 cockpit was considered “glass.” It consisted of six screens: Pilot’s PFD and ND, Co-pilots PFD and ND, and an upper and lower EICAS screen.
Behind the scenes, there is a triple autopilot system (left, center and right), two flight management computers, three flight control computers, three display control units (think SGU or symbol generator), two to three air data computers depending on customer option, and two EICAS (Engine Indicating and Caution and Advisory System) computers. There are also a large number of card files that process various system discretes to provide aural warnings.
A more modern upgrade to this, called “IS&S” keeps the same “boxes” in the shelves, but changes the PFD/ND displays to 4 LCD displays. This also got rid of the standalone airspeed indicators and altimeters (save the standby) as well as VSI’s. It makes the aircraft “NextGen” compliant.


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What would it take to bring a more efficient lifting-body airplane design (possibly a BWB) to commercial market?
I know that the MAIN reason Boeing and Airbus are held back on this is the development costs. It costs a lot to even develop a slightly new design, let alone mass manufacturing it. But that's the thing: the plane needs to be manufacturable before anything else. Also, the two persisting problems associated with BWBs (cabin pressurization and low-speed control) must be solved. What are the other things that will need to be done to make this a reality? I'm starting to get bored of the classic TAW.
My question is different in the sense that it asks for ways to actually make it happen, as I'm a firm believer that it can be done.

@user3528438 "bombs"? BWBs are supposed to be more comfortable with their larger cabin width. Also, you guys should check out https://www.facebook.com/disruptaviation/ please contribute!

No we should not. Aviation is not to be disrupted because we want to keep it safe. Disruption is to an extent carried out by military aviation.

@Koyovis Who says aviation can't be safer with a new design? There are still crashes happening around the world every year. There definitely is a room for improvement for safety.

@AhmetYeseviArslan Sorry I was interrupted when I was writing the comment, but my concern is, to implement BWB it might be necessary to add a lot of support structures into the cabin divide the internal space badly, the more blended the worse. For a bomber or tanker this isn't a problem because bomb is dense and fuel can flow so they can be stored around the support structures easily.

@user3528438 Yes, they might require more structural weight PER unit length, but since the length of the plane is almost going to be cut in half, it might require only the same amount of support structures, if not less, than TAWs. You don't need to make it too wide either. I'm thinking converting single-aisle planes with passenger capacities of 100-150 to having the same width as a wide-body is a good start. Also, sorry but I don't really get what you mean by your bomber explanation. Can't you store your fuel inside your wings, just like how it is done currently?

@qqjkztd that's really cool! I didn't even know about this. But why don't they make the fuselage in a way that provides lift on cruise as well?


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Can leaning provide more power when running at full throttle?
Looking at this graph I see that a piston engine provides less than best power when the mixture is richer than best power, and this is expected indeed.
I know that at full throttle, more than the required fuel is provided to the engine in order to achieve better cooling.
Also, I know that - especially on supercharged engines - the amount of "cooling" fuel is quite high, that is, the engine is not surely providing its best power when at full throttle.
If an engine is rated 300hp when at 29 inches of manifold pressure (MAP) and 2700RPM at full throttle, does it mean that it is actually capable of providing more power if leaned to the best power mixture? It seems to be that it should be able to provide around 8-9% more power. Of course, I would expect it to suffer some serious damage.

Yes. The engine will produce its optimum amount of power for throttle setting when leaned to the correct stoichometric mixture.   The primary risk during operation at peak EGT/TIT is of course the high temperature during operation and greater wear and tear. Engines are usually operated approximately 50° rich of peak for max performance or 50° lean of peak EGT for economy operations, depending on the model of engine, flight regiment, etc.  Rich mixtures are preferred to keep the engine cool and minimize detonation risks, but it can also foul the sparkplugs with lead deposits, reducing engine efficiency, power and causing engine roughness during operation.  Excessively lean mixtures can sip gas during cruise but risk fuel starvation or put the engine at a high risk of detonation resulting in severe damage.  For these reasons, the leaning range I stated above is the most widely used.
Normally aspirated engines are often leaned prior to high-performance operations at high altitude‘s, such a short take offs from a mountain airstrip, etc.

So it right to say that if I lean the engine at takeoff for best performance, it can produce more than its rated power?

The risk of detonation occurs with excessively high temperatures, in other words, at or near peak. The further lean of peak the engine is operated, the further that risk is reduced. The danger lies in inadvertently running the engine too hot while attempting to run lean. This can occur if the fuel system is poorly tuned and especially with insufficient temperature monitoring available (e.g. six point EGT). Excessively lean mixtures cannot and do not increase risk of detonation, but insufficient lean lean mixtures can.

Detonation is always a risk on the lean side of the stoichiometric curve and there is a notable risk of this occurring with an excessively lean mixture as well.  Some engines can operate safely at Peak EGT, though running on the richer side for cooling purposes seems to be the industry trend.


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What are the B737 MAX 8's OEW and max payload?
I have Googled it, but have not found official info on that.

The type certificate of the Boeing 737 provides the following table for the MAX:

Thanks, @DeltaLima

I have found on Jane's database 45.065kg for OEW. And MZFW is 65.950kg. Doing the math, one get 20.885kg. So, Wikipedia info is quite good.

Wikipedia gives 45,070 kg as the MAX 8's OEW and 20,882 kg as its maximum payload.

Thanks for the answer. In fact, I'm looking for oficial information. I did some math and the 737 max 8 has greater OEW than 737-800 NG. That might not be an error, but I have to check. Regards, Evandro

@Evandrojs it would make sense with bigger, heavier engines.

For sure, @fooot. But even so, it is expected weight reduction on airframe with more composites.

@Evandrojs the MAX didn't add a lot of new composites, besides the engines the only major structural changes were the improved winglets and area around the APU.

Thank you, @fooot. The weight increase looks more reasonable now.


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What are the disadvantages of a twin boom aircraft?
Not to be confused with twin fuselage design.
Especially for high wing span UAVs, twin boom design seems to be a better option as it will reduce wing bending in flight. But it is not normally used, are there any aerodynamic(or otherwise) disadvantage of this design?

The main disadvantage is flutter. The booms add a mass behind the axis of elasticity which will twist the wing when it bends. This twisting will increase the local angle of attack when the wing bends upwards and increases the bending moment, and vice versa on downward deflection. Once the plane flies fast enough, flutter is hard to avoid. The main remedy is to make the inner wing stiffer in bending and torsion, so the flutter frequency is shifted outside of the flight envelope. This costs weight, though.


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How do banner tow planes coordinate with air traffic control?
I tried searching with terms I think were correct around the net, but no satisfying results.
I have seem many times small planes circling around when there is some special event going on. They have advertising banners trailing behind them. For busy airspaces like the San Francisco bay area where you just have to glance up to spot a plane, how does this work with ATC?
Do these planes have to stay under certain level that is not controlled by ATC or ATC just allocates them a block of area and declares it off limits for others?
Do they have to declare their intention of circling special event areas given the security concerns and large gathering of people?

Related: What are the regulations involved in aerial advertising?

An aircraft conducting a banner towing operation must have prior approval (written letters of authorization) from any ATC authority they will be conducting operations prior to the banner tow operation. A copy of this letter must be carried on board the aircraft. The local FSDO must also be involved (which will handle the 7711-2 application).
The first thing you need to do is to file Form 7711-2 "Certificate of Waiver or Authorization Application" detailing all regulations which will be violated (minimum safe altitudes/separation, etc).
From the INFORMATION FOR BANNER
TOW OPERATIONS FAA/FS-I-8700-1:

Conduct all banner tow operations in VFR weather conditions defined by Title 14 of the Code of
  Federal Regulations (14 CFR) part 91, section 91.155. Operations shall be conducted only between
  the hours of official sunrise and official sunset.
The certificate holder shall obtain the airport manager’s approval to conduct banner tow operations
  at each airport of intended operation.
Notify appropriate airport officials in advance when banner tow operations will be in close
  proximity to each non-towered airport.

...
Operations outside the geographic area of the issuing FSDO will be coordinated with the appropriate
  jurisdictional FSDO in advance and the operator will comply with all special provisions imposed by
  that office.

They would coordinate with ATC beforehand to fly low & slow near congested areas.
For example, go to skyvector.com and enter KSFO and KOAK as a flight. You can see all the controlled airspace, the levels it starts at and how high it goes. I don't know where the area you are discussing is in relation to the controlled airspace

It depends what airspace they are in.  Typically most airports in major cities with class B and class C airspace have surface areas and then shelves extending out as far as 30 NM from the central airport.  Below these shelves is either Class E and Class G airspace which either will not require ATC clearance to operate in or is uncontrolled altogether.  Here, a banner tow aircraft can operate without a flight plan, or flight following with relative ease.  If you look at the airspace around San Francisco, you’ll notice that most of it are shelves, which banner tow aircraftcan fly under
If banner tow ops are necessary within the surface areas, any licensed commercial pilot may operate in these areas with the appropriate ATC clearance and be equipped with a transponder with altitude reporting capability.  Some major airports may request you pre arrange this flight with ATC prior to flight to allow controllers to anticipate flight activity by a banner towing aircraft and route their traffic accordingly.

If the pilot is not being compensated, the requirement drops down to a Private Pilot with 200 hours PIC, you don't have to be a commercial pilot necessarily.

Technically true, though very few, if any banner tow flights are private ventures.  One can more or less assume they are commercial ventures.


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Have there been any incidents caused by an inability to shut down an engine?
I read many items on the avherald.com site where it says "engine shut down during flight" or words to similar effect.
I'm wondering if there are any instances where an engine could not be shut down or the pilots had trouble shutting down the engine when commanded. What sort of backup systems are in place to avoid this kind of scenario?

Fuel valves will reliably shut down any combustion engine. So will an empty tank.

@PeterKämpf, Agreed, but a jet engine that can not be stopped on time while on the ground could also cause lot of issues.

I distinctly recall at least one serious accident where a timely evacuation would have saved all lives, but for the inability to shut down an engine: either this slowed the evac, or they chose to delay the evac while they futzed with the uncooperating engines.

@PeterKämpf The thing on large jets is that fuel valves are electrically operated. A common issue with many jets is that if the power supply to the HP valve is lost, shutdown with the LP valve will take some time (60 seconds at idle on the A320), and have a tendency to damage the HP fuel pump.

@Harper Link / source?

@Harper I recall some accidents where an engine fire meant some of the emergency exits could not be used but not an inability to shut down an engine.

Probably Saudia 163. The fact that the cabin remained pressurized and engines running was likely a side effect of crew incapacitation, and not an inability to shut down the engines. I think it's unfounded to say that fatalities would be avoided if engines were shut down; fatalities could be avoided if the incident was handled with urgency. The poor CRM and captain's approach to the emergency was the root cause.

@user71659 I can imagine that if it is an emergency situation, I'd be happy for the HP pump to take some damage - it can be fixed, lives can't.

Does https://en.wikipedia.org/wiki/Cornfield_Bomber count? Incident: pilot ejected. Problem: no-one available to shut down engine/pilot could not accept command to shut down engine. Result: landed in a corn field and was avoided by locals until it ran out of fuel

@user71659: IIRC, the final transmission from the aircraft occurred after ATC had already started asking the crew to shut down their engines, strongly indicating that they were not yet incapacitated at that point.

Qantas Flight 32
Enroute to Sydney, Engine Number 2 of the A380 disintegrated explosively. The shrapnel of the explosion destroyed many systems, including a hydraulic system, the anti-lock braking system, flaps and electronic controls.
After emergency landing, the pilots were unable to stop engine number 1, because the controls had been destroyed by shrapnel. Emergency services had to douse the engine until flameout was achieved.

Source

What was the cause of the Engine 2 spontaneous combustion?

@Cloud I believe it was a cracked fanblade that caused catastrophic failure.

@Cloud: Per the Wikipedia page, which matches my memory for the period (I'm interested in engines), it was a miss-bored oil pipe in the engine, which cracked due to metal fatigue, starting an oil fire, which led to the failure of the intermediate-pressure turbine disc.

@Cloud As John said, it was a faulty oil-pipe that burst in-flight. The oil flowed into the turbine and started burning, acting like fuel and accelerating the turbine blades to a supersonic speed. At some point the load on a turbine disc was too much and it exploded. There is a very good Mayday episode about the Qantas Flight 32.

@NoahKrasser Hi Noah, I have a fof, so don't think I should watch that xD

@Cloud It actually shows how safe flying is today and that aircraft are still able to fly even though around 50 systems got destroyed. Maybe it helps :)

I'd argue that this incident wasn't caused by an inability to shutdown the engine. It was a side affect, and it caused problems after landing, but the cause was the other engine exploding.

Cathay Pacific flight 780 on 13 Apr 2010
Fuel contaminated by super absorbent polymer jammed fuel valves caused engine control problems. The aircraft eventually landed with one engine at about 70% N1 at significantly higher than normal airspeed, burst some tires from the increased braking necessary and was evacuated.

AFAIK, this wasn't strictly an "unable to shut down engine" but a loss of thrust control instead. One engine got stuck at 70% N1 and the other got stuck at 17% N1. For obvious reasons, the pilots kept the engines running until after landing, at which time both successfully shut down.

@user71659, on the other hand it was an accident directly caused by the inability to control thrust as opposed to the others where the inability to shut down the engine was a result of the accident.

Etihad Airbus A340-600
This famous crash happened on the acceptance engine run-up test. The causes were unrelated to engine problems, but after the crash, due to damages, two engines couldn't be shut down. One of them ran for 9 hours (!) after the incident, until it ran out of fuel, creating obvious hazard for the emergency crew. (Luckily, there were no passengers to evacuate).

There is this business jet with two engines that didn't quit for 20min after it overran the runway and splashed around in a Bay. Investigators found it attempted the landing with a 10kt tailwind on too short of field and the touchdown too far beyond the threshold.

May 15, 2005, in Atlantic City, NJ , USA

If memory serves, it wasn't just a long tailwind landing, but a long tailwind landing on a runway too short for the aircraft (and which was specifically designated off-limits to jet aircraft in the A/FD).

I don't think the mfg has approved it for water taxing either.

Air France 72.12 Sept 1993. Aircraft (747-400) went off the runway in Papeete. Due to electrical damage (aircraft nose was in the water) the engine could not be shut down from the cockpit and AFRS had to 'drown' the engine by hosing a lot of water into the inlet.
My understanding is that the failure mode of engines is to be fail-safe, ie to minimise the impact of failure. With FADEC (full authority digital engine control) the problem is what would be the best action if signal were to be lost from the control box to the engine? It was explained to me that the lesser of two evils will be to have the engine running rather than shutting down so the protocols were designed accordingly.
While this does not answer your question on backup..It is more sense if you look at it from a different angle.."what is the backup in case control of engines is lost". In this case the backup would be the engine would continue to run rather than shut down.. If this happenned in the air you would be better off with a working (albeit uncontrollable) engine rather than a dead one.

"If this happenned in the air you would be better off with a working (albeit uncontrollable) engine rather than a dead one." I'm not sure whether that holds up for multi-engine domestic flights, but there are plenty of scenarios (say, a trans-atlantic flight) where you absolutely prefer an uncontrolled but still powered engine over a dead one.

And Papeete involves quite a long water crossing, so...

@Mast I would think that if your machine can't land with an uncontrolled engine, you could always circle until you run out of fuel, whereas if the engine just shuts off then you'd better have a landing strip of some kind within your glide radius.

What sort of backup systems are in place to avoid this kind of scenario?

As I understand it airliners normally have a "fire handle" for each engine which is independent from the normal engine controls. This handle can be used to cut off fuel to the engine and optionally discharge the fire extinguishers.
I can't seem to find an official source but from what I can gather the fire handle did not work in the Quantas case, likely due to the severe damage from the uncontained failure of the other engine on the wing.

Is the fire handle placed at the interior or exterior of the plane?

@Mast It's the kind of thing you really want accessible from the interior if at all possible since getting to an exterior one in flight requires having Tom Cruise aboard, and if you're on the ground then you generally have a fire crew nearby and won't really need it.

@Perkins Since it sounds like a measure of last resort, I imagined it being as close to the motor as possible. So I had to ask :-)

@Mast Engine fires can get really hot.  It at least needs to be far enough back that you can reach it without melting your skin off.  That's why the emergency shutoff valves at fuel stations are 30 feet or more from the pumps.

In addition to the posts above, it is worth pointing out that this exact scenario is part of the flight testing of any new aircraft. If you can find it, there is a whole episode of the PBS show on the B777 that shows this test being carried out.
It was an especially odd one, because the aircraft had P&W engines and brakes designed to handle that, but they wanted to test the performance as if it was equipped with the more powerful RR engines. The chief pilot originally said no, but as the engineers at the various companies said ok, he relented.
The test required the aircraft to go to maximum power, in this case higher than the official rating so they could test the RR case. After it reached a certain speed, they put on full brakes, with the engines still at max power. When it finally came to a stop, the brakes were bright yellow. It then had to sit for a time (5 minutes IIRC) to simulate the emergency vehicles arriving, which then sprayed the brakes with water. It was quite impressive.
As they were careful to say, the idea of the test is not to pass some requirement, but to simply give future pilots an understanding of what to expect in the case it happened.


text:
How does Air Traffic Control know a flight's route and destination?
I am trying to find out in layman's terms how does ATC determine the direction a flight has to take after takeoff, or when should it start descending for the destination airport. I understand it has to do with the flight plan but Googling revealed lot of technical stuff that I couldn't understand. In my limited experience of listening to LiveATC and YouTube video, ATC never inquired about the destination - it felt like they already knew.
Is destination information always available on the screen to ATC or does the flight crew request changes based on their flight plan? How does it work when you cross international boundaries? Is the same flight plan available to ATC in all the countries the flight will be flying through?
For example, a flight taking off from SFO could be northbound towards Seattle or southbound to LA or eastbound. ATC has to make room for the proper direction of the flight and hence needs to know the destination.
To complicate matters, I have seen flights taking different routes while the destination is same e.g. one SFO-FRA flight hugged the west coast (magnificent views of the coastline) up to Canada before making a right turn, whereas other times - but with the same flight number - it kind of crosses the continental United States diagonally. So I feel it's not just about the destination, there are other factors involved.

Related: How can an ATC choose the right flight level and heading for airplanes?

Under instrument flight rules (which all scheduled passenger flights operate under), the pilot will file a flight plan with the local air traffic control authority (in the US, that is the FAA). This flight plan describes in fairly specific terms where the pilot intends to fly, by going from point to point. You can see flight plans on a site like https://flightaware.com.
These flight plans are entered (electronically, in most cases, but sometimes typed in) into the air traffic control system. So each controller who handles the flight knows where it is supposed to go next.
The details of the start and end of the flight isn't determined by the pilot, but by ATC when they set up the departure or arrival. These are done using instructions called SID (Standard Instrument Departure) and STAR (Standard Terminal Arrival Route). Depending on the traffic patterns around each airport, ATC may assign a particular SID or STAR. These instructions are like "fly at this altitude until this point, turn right, descend to this other altitude, fly until you get to this other point", and so on.
For international flights, the flight plans are transmitted from one country to another using AFTN (Aeronautical Fixed Telecommunications Network). So each country that the flight flies over knows where it is supposed to be going.
Other factors which can influence the actual route a flight takes can include:

Weather
Other air traffic
Military operations
International agreements (or more specifically, disagreements)

For example a flight taking off from SFO could be north bound towards Seattle or South bound to LA or east bound. ATC has to make the room for the proper direction of the flight and hence need to know the destination.

All airplanes wanting to fly IFR have to put in a IFR flight request.  This will necessarily have the origin and destination as well as the approximate departure time.  But the request will also have a path between (by specifying intermediate waypoints and/or airways) and a cruising altitude.
Before takeoff, ATC will then clear the airplane for a particular path (which may be somewhat different from that initially filed).  (If you listen to "clearance delivery" frequencies, you can hear these being used).  Assuming the pilot accepts the clearance, ATC and pilots now agree on the path that will be flown.
Once in the air (assuming no emergencies) pilots will need to request if they want any changes to the flight plan (perhaps to detour around weather, or to find a more comfortable cruising altitude).

VFR flight (non-airlines): Often times, we just tell ATC, no flight plan required; flight following can be requested while enroute.  For example, I have flown from my home airport west of the Boston Class B southeasterly down to Cape Cod (Nantucket Island in this case).  I took off, contacted Boston Approach while climbing, and requested flight following. They ID'd me via radar/ADB-S, gave me a squawk code, and noted the altitude I was climbing to.  Several miles later, we were handed off to a different sector, then a 3rd, maybe even a fourth. As I changed frequencies for each, I checked in, told them the altitude I was at, and that I was landing Nantucket.  Eventually I was handed off to Nantucket tower about 10 miles out.
Other times, we have depart from a towered airport. Before taking the runway, you contact the tower and let them know your desired route of flight and altitude after takeoff. Tower will tell you the direction to turn after takeoff to work you into any other traffic in the area if needed, otherwise straight out, or left or right turns away from the airport are approved, and any restrictions needed to keep you away from other aircraft if needed.

For IFR, the desired route is in the flight plan, which is almost always filed ahead of time. When an aircraft is ready for departure, ATC assigns them a transponder code (squawk) that is linked to their call sign, which is in turn linked to their flight plan. As they move from one controller to the next, that all gets passed along. Occasionally the squawk will change as they move (there are only 4096 codes, so the code you get here may already be in use over there), but the new one is then linked to the callsign and therefore your flight plan.
For VFR, flight following is (basically) when you get a squawk from ATC without a flight plan, so you're responsible for your own navigation. That still gets you the benefit of traffic advisories, but more importantly, if you run into trouble, they already know who and where you are so they can help you a lot faster than some random callsign they know nothing about.
(You can file a VFR flight plan, but ATC won't use it; it's just a hint where to look for wreckage if you don't arrive at the destination, which doesn't seem all that useful to the pilot. Prepare one for your own planning on long trips, sure, but instead of filing it just get flight following.)


text:
Is TBO an airworthiness item or just a recommendation?
In browsing Trade-a-Plane for my dream (light GA) ride, I often note the TBO (Time Before Overhaul) for an aircraft in relation to its asking price.  Obviously, the more time left before an overhaul is due, the greater the value of the airplane compared to one that is near or beyond its overhaul due date (hours).
I've always assumed this was an airworthiness item, meaning the aircraft was illegal to fly if it was overdue for a major overhaul.  But now I'm not so sure.  I've seen aircraft advertised as having a relatively recent top overhaul while being overdue for a major overhaul and I've seen a couple advertised that were overdue with no recent work done. Is a GA aircraft legal to fly if it's overdue for maintenance, and what are the exact rules for this?

Aircraft are not illegal to fly after TBO, usually if the compressions are good and oil screens come back clear, flying beyond TBO is perfectly fine. Some people prefer it since a well cared-for engine near TBO is less likely to fail than one that has just been taken apart. TBO is purely manufacturer recommendations, and going beyond is a pretty controversial topic. Unless you are talking about commercial/passenger operations then there may be regulations to abide by.

In general, for part 91, TBO is no more than a recommendation. I would rather fly an an engine at TBO that has been operated continuously and has been well maintained than fly a 100 hr engine that has been operated very little in the last few years. A good engine can easily go to 3-4000 hrs—or even 6000+ hrs—if flown properly and well maintained. I am in the middle of overhauling a small 6 cylinder at 150 hrs that was operated very little in the last 10 years. It just depends. Another consideration is to merely replace cylinders, which is a cheap, but sometimes effective "overhaul".

Unless there is a TBO Airworthyness Directive for that particular engine/airframe/serial number, it is not illegal for GA operations to fly beyond TBO. I can't find an example of a TBO AD but I do remember seeing some.
TBO is a manufacturer recommendation for that particular engine, and does not have any legal enforcement with the FAA. An engine that is well cared-for and has good compressions and clear oil screens (along with other positive inspections) is perfectly fine to fly beyond TBO. There are even stories of people flying 1000 hours or more beyond TBO.
Here are some good reads from around the web:
The Savvy Aviator - Debunking TBO
AOPA Engine Overhauls
Aviation Law - Flying Past TBO, Negligence or Smart Economics
In any case, flying beyond TBO is controversial. Some say that an engine near or over TBO is less likely to fail than one that has been recently taken apart, or at least less likely to fail suddenly.
The key aspect though when buying used aircraft is you don't know how the engine was treated in its run up to TBO. Was it shock cooled? Used for training? Operated out of a grass strip? Poor maintenance? Flown rarely? There are way too many conditions to consider when buying an aircraft near TBO to make the judgement of going beyond it safely or not. The only person who can answer that question is an A&P. That is why TBO is tied so closely to the value of an aircraft. Engine overhauls are expensive, running $25k or more.

Your last paragraph talks about knowing how the aircraft was flown and maintained. Wouldn't the log book be a pretty good indicator of that? As I understand it, it would show flight frequency, maintenance events, destinations, etc. (Hope this doesn't wander into the realm of "whole new question".)

Destinations no,  only hours are recorded in airframe, engine, and prop logs. It's not going to tell you if it was training or cross country, easy hours or hard primary training ones. Logs say the maintenance was done, but not the quality of it. Was oil topped off or ran low between changes? Etc...

Great answer and I learned a lot from the links too.  Thanks!

@FreeMan An aircraft logbook is only as good as the people who make entries in it. For me, looking at logbooks is good for things like checking for AD and SB compliance, and looking for major repairs, or indicators of problems. When buying an aircraft, nothing beats a thorough inspection done by someone you trust who is familiar with the aircraft type.


text:
How strongly is airband affected by severe thunderstorms in practice?
In light of this question I was very surprised to learn that despite operating on a higher frequency (108 MHz upwards) than the standard FM broadcasting, airband uses amplitude modulation (AM) instead of the much more robust frequency modulation (FM).
While amplitude modulation allows several senders/receivers to use the same channel and prevents jamming by the capture effect of FM, amplitude modulation should allow lightning strikes to disturb reception.
In Review of Measurements of the RF Spectrum of Radiation from Lightning by David M. Le Vine, NASA Technical Memorandum 87788 we see this chart in Figure 5:

I know that the AM broadcast band around $10^3$ kHz is severely disturbed in thunderstorms; airband is near $10^5$ kHz, so the noise should be being damped by a factor of -25dB (~ factor 1:300).
How is radio reception affected in practice?

Have any of you pilots or air traffic controllers ever noticed noise from thunderstorms on the radio?

In my personal experience, lack of good static discharge has had the most effect in communication.

@rclocher3 (and OP), very much yes, lightning strikes are very noticeable as a loud burst of white noise ("static") that breaks through the radio's squelch function. I can't say as I've noticed any difference in reception range though.